Marine pipe laying system, method and hoisting device

ABSTRACT

The invention relates to marine pipe laying. For laying of an offshore pipeline, a system is used having a hoisting device. The hoisting device comprises a tower with a tower top side provided with cable pulleys. Furthermore the hoisting device has a traveling block which is displaceably attached to the tower. The traveling block comprises a first block and a second block, both provided with cable pulleys. The first block is provided with a clamp for holding a pipe section to be connected to the pipeline as well as for lowering the pipeline after the pipe section is connected to the pipeline. The hoisting device has a hoisting cable and a winch, the hoisting cable being guided over the cable pulleys on both the tower top side and the traveling block. The traveling block is moveable with respect to the tower by operation of the hoisting winch. The first block and the second block are adapted to be releasably coupled, in which coupled state they can travel along the tower as a unit and are able to support the weight of the pipeline. The second block can be locked to the tower, such that the first block can travel along the tower while the second block remains stationary with respect to the tower.

The present invention relates to a marine pipe laying system for layingof an offshore pipeline, the system comprising:

a) a main supporting structure;

b) a pipe connecting station, wherein a pipe section is connected to anuppermost end of a previously launched pipeline;

c) a static clamp adapted for releasably securing the uppermost end ofthe previously launched pipeline, wherein the static clamp is adapted tosupport the weight of the previously launched pipeline;

d) a hoisting device comprising:

a tower with a tower top side provided with cable pulleys,

a traveling block which is displaceably attached to the tower and whichis provided with cable pulleys and a traveling clamp for holding a pipesection to be connected to the pipeline as well as for lowering thepipeline after the pipe section is connected to the pipeline,

hoisting means comprising a hoisting cable and a winch, the hoistingcable being guided over the cable pulleys on both the tower top side andthe traveling block, wherein the traveling block is moveable withrespect to the tower by means of the hoisting means.

Such a system is known e.g. from U.S. Pat. No. 5,421,675. The travelingblock has to be able to support the pipeline during launch of thepipeline, which in practice means that the traveling block has to beable to support a load of 1000 tons or more. To this end the travelingblock and the tower top side have to be provided with enough cablepulleys to guide the hoisting cable in order to create enough cableparts extending between the traveling block and the tower top side, theload being distributed over the parts. However, the more cable partsextend between the traveling block and the tower top, the slower theblock can be moved along the tower.

When laying a pipeline the application of a hoisting system with enoughcable parts is necessary to support the load of the pipeline, but it hasthe drawback that when the load is released from the traveling block,the traveling block can only be moved upwards relatively slowly, whichlimits the length of pipe to be laid in one day.

The object of the invention is to provide an improved pipe layingsystem.

This object is achieved by a pipe laying system according to thepreamble of claim 1, wherein the traveling block comprises a first blockand a second block, both provided with cable pulleys, the travelingclamp being attached to the first block, wherein the first block and thesecond block are adapted to be releasably coupled, in which coupledstate they can travel along the tower as a unit and are able to supportthe weight of the pipeline, and wherein the system comprises lockingmeans for locking the second block to the tower, such that the firstblock can travel along the tower while the second block remainsstationary with respect to the tower.

With this pipe laying system a pipe laying method according claim 8 canbe performed, which method comprises the following steps:

-   -   i) holding the uppermost end of the pipeline and supporting it        with the traveling clamp with the traveling block in an        uppermost position on the tower,    -   ii) lowering the pipeline by lowering the coupled first block        and second block by means of the hoisting means to a lowermost        position on the tower,    -   iii) gripping the uppermost end of the pipeline with the static        clamp,    -   iv) releasing the traveling clamp from the pipeline,    -   v) locking the second block to the tower by means of the locking        means,    -   vi) hoisting the first block from the lowermost position to the        uppermost position by means of the hoisting means,    -   vii) gripping the uppermost end of a pipe section to be        connected to the pipeline with the traveling clamp,    -   viii) lowering the first block with the pipe section by means of        the hoisting means such that the lowermost end of the pipe        section can be gripped and lined up with the uppermost end of        the pipeline at the pipe connecting station,    -   ix) releasing the traveling clamp from the pipe section,    -   x) unlock the second block from the tower,    -   xi) connecting the lowermost end of the pipe section to the        uppermost end of the pipeline,    -   xii) hoist the second block to the uppermost position while the        pipe section is connected to the pipeline,    -   xiii) couple the first block and second block,    -   xiv) grip the uppermost end of the pipe section with the        traveling clamp,    -   xv) release the pipeline from the pipe connecting station and        from the static clamp, while holding the uppermost end of the        pipeline and supporting it with the traveling clamp with the        traveling block in an uppermost position on the tower.

With the described system and method the first block with the travelingclamp and the second block can be moved upwards separately when thelaunched pipeline is supported by the static clamp. Since the secondblock remains locked with respect to the tower, the moving portion ofthe traveling block, i.e. the first block has less cable parts extendingbetween it and the top side of the tower. This leads to a higherhoisting speed of the first block with respect to the case where thewhole traveling block would be hoisted up as a unit. This results inthat the traveling clamp is quicker available at the top side of thetower in order to grip a new pipe section to be connected to thepipeline hanging off the static clamp. The first block positions thelowermost end of the pipe section at the pipe connecting station, afterwhich it is gripped by line up means that line up the pipe section withthe uppermost end of the pipeline and the traveling clamp can bereleased. Simultaneous to the connecting operation the second block isunlocked from the tower and hoisted up. By the time the pipe section isconnected to the pipeline, the second block is at the uppermost positionand coupled to the first block, whereby the traveling block as a unit isready for gripping the uppermost end of the pipeline and lowering it.

With the system according to the invention the first block with thetraveling clamp can be available at the uppermost position within 17% ofthe time necessary for a non splittable traveling block to be availableat the uppermost position. With the method and system according to thepresent invention valuable time is saved with respect to pipe layingmethods according to the prior art which results in a significantdecrease of costs.

Another aspect of the invention relates to a hoisting device accordingto claim 11, the hoisting device comprising:

a tower with a tower top side provided with cable pulleys,

a traveling block which is displaceably attached to the tower and whichis provided with cable pulleys and holding means for holding a load,

hoisting means comprising a hoisting cable and a winch, the hoistingcable being guided over the cable pulleys on both the tower top side andthe traveling block, wherein the traveling block is moveable withrespect to the tower by means of the hoisting means. The traveling blockcomprises a first block and a second block, both provided with cablepulleys, the first block being provided with the holding means,

wherein the first block and the second block are adapted to bereleasably coupled, in which coupled state of the first block and secondblock a higher load can be supported than in an unlocked state and inwhich coupled state of the first block and second block they can travelalong the tower as a unit,

and wherein the second block is provided with locking means for lockingit to a lower side of the tower, such that the first block can travel inan upward direction along the tower while the second block remainsstationary with respect to the tower.

With such a hoisting device according to claim 11 a method comprising anoperation cycle can be performed in which:

a first load is gripped by the traveling clamp with the traveling blockconsisting of the coupled first block and second block in an uppermostposition on the tower;

the first load is lowered by lowering the coupled together first blockand second block by means of the hoisting means to a lowermost positionon the tower where the traveling clamp is releasde from the first loadwhich is handed over to a load handling device;

wherein the second block is locked to the tower by means of the lockingmeans, the first block alone is hoisted from the lowermost position tothe uppermost position by means of the hoisting means, after which thefirst block is used for an intermediate operation after which the secondblock is unlocked from the tower and hoisted to the uppermost positionwhere it is coupled to the first block.

The hoisting device is thus well adapted for performing a operationcycle wherein in an intermediate operation step only the first block hasto be available at the top side of the tower for taking part in anintermediate operation which does not require the full load supportingcapacity. The first block can thus be used to deliver an intermediateload to a load handling device. When the first block is released fromthe intermediate load and the intermediate load is being handled by theload handling device, the second block can return to the uppermostposition. When the time period necessary to handle the intermediate loaddoes not exceed the time necessary to hoist up the second block, thecycle time can be significantly reduced.

Such a hoisting device according to claim 11 can further advantageouslybe used in a method for connecting a first object and a second object ata connecting station. The method comprises the following steps:

-   -   i) holding the first object and supporting it with the traveling        clamp with the traveling block in an uppermost position on the        tower,    -   ii) lowering the first object by lowering the coupled first        block and second block by means of the hoisting means to a        lowermost position on the tower,    -   iii) gripping the first object with gripping means at the        connecting station,    -   iv) releasing the traveling clamp from the first object,    -   v) locking the second block to the tower by means of the locking        means,    -   vi) hoisting the first block from the lowermost position to the        uppermost position by means of the hoisting means,    -   vii) gripping with the traveling clamp the second object,    -   viii) lowering the first block with the second object by means        of the hoisting means such that the second object is delivered        to the connecting station and gripped by its gripping means,    -   ix) releasing the traveling clamp from the second object,    -   x) unlock the second block from the tower,    -   xi) connecting the second object to the first object,    -   xii) hoist the second block to the uppermost position while        connecting the second object to the first object,    -   xiii) couple the first block and second block,    -   xiv) grip the connected first and second object with the        traveling clamp,    -   xv) release the connected first and second object from the        connecting station, while holding them with the traveling clamp        with the traveling block in an uppermost position on the tower.

The invention will be described in more detail in the followingdescription of a preferred embodiment with reference to the accompanyingdrawing. In the drawing

FIG. 1 shows a schematic side elevational view of a pipe laying system,and

FIGS. 2-7 show a schematic front view of a pipe laying systemillustrating the steps of a pipe laying method.

The embodied system relates to a vertical or near vertical pipelinelaying technique, such as the J-lay technique, for a pipeline launchedfrom a vessel in an essentially vertical orientation. The systemprovides an improved pipe laying system for vertical or near verticalmarine pipelaying, particular in deep water.

The methods illustrated with reference to the FIGS. 1-7 relate to anefficient method for the vertical or near vertical laying of offshorepipelines.

The pipe laying system provides a-vessel which acts as a main supportingstructure. In FIG. 1 and FIG. 2 a part of this vessel is shown andindicated by reference numeral 1. In the FIGS. 2-7 the vessel 1 isomitted for the reasons of clarity of the drawing.

On the vessel 1 is provided a hoisting device indicated by referencenumeral 2. The hoisting device 2 comprises a tower 3 with a tower topside 3 a. On the tower top side 3 a are provided cable pulleys 4.

The hoisting device 2 further comprises a traveling block 5 which isdisplaceably attached to the tower 3. The traveling block 5 is providedwith cable pulleys 6 and 7.

Also the hoisting device has hoisting means comprising a hoisting cable8 and a winch 9. The hoisting cable 8 is guided over the cable pulleys 4at the top side 3 a of the tower 3 and the cable pulleys 6, 7 on thetraveling block 5. By winding up and unwinding the cable 8 on and offthe winch 9, the traveling block 5 is moveable with respect to the tower3.

As can be seen best in FIG. 2 the traveling block 5 comprises a firstblock 51 and a second block 52. In the particular embodiment that isshown in the figures, the first block 51 is provided with two cablepulleys 6. The second block 52 is provided with four cable pulleys 7.

The first block 51 is provided with a traveling clamp 10 being attachedto it. The traveling clamp 10 is adapted to grip the upper end of asingle pipe section 20 or a pipeline 21 which will be described in moredetail below.

The second block 52 has a substantially ring shaped body 52 a withcentral opening 52 b (see FIG. 3). The first block 51 has a body 51 awith a diametrical dimension exceeding the diametrical dimension of thecentral opening 52 b of the second block 52, such that the first block52 cannot pass through the opening 52 b of the second block 52. Thesecond block 52 has a supporting surface 52c facing upwards andsurrounding the central opening 52 b for engagement with the first block51 and for supporting it. The first block 51 and the second block 52 canbe coupled together. In the coupled state, which is shown in FIG. 2, thefirst block 51 engages the supporting surface 52 c. In the coupled statethe first block 51 and second block 52 form a unit and are able tosupport together the weight of a load held by the traveling clamp 10.This load can be the load of a pipeline hanging off which can amount upto 1000 tons. The unit, or better the traveling block unit, formed bythe coupled first block 51 and second block.52 can travel along thetower 3 by operation of the winch 9.

The structure of the traveling block 5 is such that the first block 51and the second block 52 can be separated. Thereto the second block 52can be locked to a lower part of the tower 3 by means of suitablelocking means, preferably locking pins 13. The locking pins 13 can bearranged on the second block 52 such that they upon a suitable controlsignal move towards an extended position and extend into locking holesprovided in the tower 3. It is also possible to provide the tower 3 withthe pins 13, which upon a suitable control signal move towards anextended position and extend into locking holes provided in the secondblock 52.

Locking of components with locking pins and locking holes is a generallyknown locking mechanism. It is to be understood that in the above bylocking means not only the preferred locking pins and locking holes aremeant, but also any other suitable locking mechanism are meant like theones mentioned here, such as e.g. bolt/nut combinations, cylinders,clamps etc.

When the second block 52 is locked to the tower 3, the first block 51can travel along the tower 3 while the second block 52 remainsstationary with respect to the tower 3.

The pipelaying system is furthermore provided with a pipe connectingstation, more in particular a pipe welding station 14 for welding thelowermost end of a pipe section 20 to an uppermost end of a previouslylaunched pipeline 21. In addition the pipe laying system has a line uptool 16 for linig up the lowermost end of a pipe section 20 with theuppermost end of the pipe line 21 such that they can be welded togetherin the welding station 14. Also, the pipelaying system has a staticclamp 15, in the art also know as a hang off clamp for gripping an upperend of the pipeline 21 and which is adapted to support the load of thepipeline 21. These components will become more apparent in the followingdescription of a pipe laying method.

In FIG. 2 is shown a first state wherein the first block 51 and secondblock 52 are coupled and the traveling clamp 10 is holding the uppermostend of the pipeline 21 and supporting the load of the launched pipeline21. Then the static clamp 15 will grip the upper end of the pipeline 21and take over the load of the pipeline 21, after which the travelingclamp 10 can be released from the pipeline 21.

Next, the second block 52 can be coupled to the tower 3 by means of thelocking pins 13. As is illustrated in FIG. 3, this locked state of thesecond block 52 allows the first block 51 to be hoisted up by operatingthe winch 9 while the second block 52 is retained by the locking pins 13at its lowermost position on the tower 3.

At the moment that the first block 51 has arrived at its uppermostposition at the tower 3 a new pipe section 20 is delivered to the tower3 by means of suitable pipe delivering means. This new pipe section 20is then gripped at its upper end by means of the traveling clamp 10 asis shown in FIG. 4.

The pipe section 20 can be lowered over such a distance that it can begripped by the line up tool 16, after which the traveling clamp 10 canbe released from the pipe section 21. This state is shown in FIG. 5.Next the pipe section 20 can be lined up with the pipeline 21 hangingoff the static clamp 15 before their respective ends are welded togetherin the welding station 14.

As is shown in FIG. 6, during the welding operation the locking pins 13are released and the second block 52 is hoisted towards its uppermostposition by operation of the winch 9. Preferably the system is designedsuch that hoisting the second block 52 to its uppermost position takesnot more than the time necessary to weld the pipe section 20 and thepipeline 21 together. In such a way the intermediate time, during whichthe hoisting system is not necessary to carry a load, is usedefficiently to join the first block 51 and second block 52.

In FIG. 7 is shown the state in which the second block 52 has arrived atits uppermost position on the tower 3 and is joined together with thefirst block. In this state the traveling clamp 10 grips the upper end ofthe pipeline 21. Because the unit 5 formed by the first block 51 andsecond block 52 is able to support the load of the pipeline 21, thestatic clamp 15 is released from the pipeline 21 and the pipeline 21 islowered by operating the winch 9 until the state depicted in FIG. 2 isreached. This cycle is repeated to lay the pipeline 21.

In this example the first block 51 has two cable pulleys 6 and thesecond block 52 has four cable pulleys 7. As a result four cable parts 8a-8 d extend between the top side 3 a of the tower 3 and the first block51, and eight cable parts 8 e-8 i extend between the top side 3 a of thetower 3 and the second block 52 (see FIG. 3). This implies that inprinciple the first block 51 can be hoisted up in one third of the timethat would be necessary if a non-splittable traveling block with twelvecable parts would be applied. This means that with the particularhoisting system shown in the figures the traveling clamp 10 is availableat the top side 3 a of the tower 3 much quicker for gripping a lightload, i.e. a single pipe section 20. The intermediate time necessary toconnect the pipe section 20 to the pipeline 21 is efficiently used tomove the second block 52 upwards to bring the hoisting system to itsfull supporting capacity which is necessary to lower the pipeline 21.

With the present pipe laying system a considerable amount of time can begained. This leads to a considerable reduction of the overall time ofuse of pipe laying equipment and thus in pipe laying costs.

It is to be understood that the invention is not limited to theparticular embodiment illustrated in the figures. The invention can beperformed and practiced in various ways. The invention can thus beapplied with other pipe laying methods with a more inclined launchdirection than the one illustrated in the above, even almost horizontallike S-lay. Also the application of the hoisting system is not limitedto a pipe laying method, but could also be applied for other operations,e.g. offshore drilling.

In the embodiment of the pipe laying system shown in FIGS. 1-7 the firstblock 51 cannot pass through the central opening in the second block 52.A traveling block structure is however envisaged wherein the first blockand second block can be coupled in another manner, e.g. by locking pinsor the like, wherein the first block can pass the second block fromabove or below.

1. A marine pipe laying system for laying of an offshore pipeline, thesystem comprising: a) a main supporting structure; b) a pipe connectingstation, wherein a pipe section is connected to an uppermost end of apreviously launched pipeline; c) a static clamp adapted for releasablysecuring the uppermost end of the previously launched pipeline, whereinthe static clamp is adapted to support the weight of the previouslylaunched pipeline; d) a hoisting device comprising: a tower with a towertop side provided with cable pulleys, a traveling block which isdisplaceably attached to the tower and which is provided with cablepulleys and a traveling clamp for holding a pipe section to be connectedto the pipeline as well as for lowering the pipeline after the pipesection is connected to the pipeline, hoisting means comprising ahoisting cable and a winch, the hoisting cable being guided over thecable pulleys on both the tower top side and the traveling block,wherein the traveling block is moveable with respect to the tower bymeans of the hoisting means, characterized in that the traveling blockcomprises a first block and a second block, both provided with cablepulleys, the traveling clamp being attached to the first block, whereinthe first block and the second block are adapted to be releasablycoupled, in which coupled state they can travel along the tower as aunit and are able to support the weight of the pipeline, and wherein thesystem comprises locking means for locking the second block to thetower, such that the first block can travel along the tower while thesecond block remains stationary with respect to the tower.
 2. The systemaccording to claim 1, wherein the locking means are adapted to lock thesecond block in a lowermost position at a lower side of the tower, suchthat the first block can travel in an upward direction towards anuppermost position along the tower while the second block remainsstationary with respect to the tower.
 3. The system according to claim2, wherein the hoisting means are adapted in such a way that the traveltime of the single second block from its lowermost position to itsuppermost position on the tower is less or at most equal to the time toconnect the pipe section to the pipeline.
 4. The system according to anyof the claims 1-3, wherein the locking means comprise one or morelocking pins moveable between a locked position into a locking hole andan unlocked position.
 5. The system according to claim 4, wherein theone or more locking pins are-arranged on the second block and thelocking holes are arranged on the tower.
 6. The system according toclaim 4, wherein the one or more locking pins are arranged on the towerand the locking holes are arranged on the second block.
 7. The systemaccording to any of preceding claims, wherein the pipe connectingstation comprises a welding station.
 8. A method for laying of anoffshore pipeline, wherein use is made of a system comprising: a) a mainsupporting structure; b) a pipe connecting station, wherein a pipesection is connected to an uppermost end of a previously launchedpipeline; c) a static clamp adapted for releasably securing theuppermost end of the previously launched pipeline, wherein the staticclamp is adapted to support the weight of the previously launchedpipeline; d) a hoisting device comprising: a tower with a tower top sideprovided with cable pulleys, a traveling block which is displaceablyattached to the tower and which is provided with cable pulleys and atraveling clamp for holding a pipe section to be connected to thepipeline as well as for lowering the pipeline after the pipe section isconnected to the pipeline, hoisting means comprising a hoisting cableand a winch, the hoisting cable being guided over the cable pulleys onboth the tower top side and the traveling block, wherein the travelingblock is moveable with respect to the tower by means of the hoistingmeans, the traveling block comprising a first block and a second block,both provided with cable pulleys, the traveling clamp being attached tothe first block, wherein the first block and the second block areadapted to be releasably coupled so as to travel along the tower as aunit, and wherein the system comprises locking means for locking thesecond block to the tower, such that the first block can travel alongthe tower while the second block remains stationary with respect to thetower, the method comprising the following steps: i) holding theuppermost end of the pipeline and supporting it with the traveling clampwith the traveling block in an uppermost position on the tower, ii)lowering the pipeline by lowering the coupled first block and secondblock by means of the hoisting means to a lowermost position on thetower, iii) gripping the uppermost end of the pipeline with the staticclamp, iv) releasing the traveling clamp from the pipeline, v) lockingthe second block to the tower by means of the locking means, vi)hoisting the first block from the lowermost position to the uppermostposition by means of the hoisting means, vii) gripping the uppermost endof a pipe section to be connected to the pipeline with the travelingclamp, viii) lowering the first block with the pipe section by means ofthe hoisting means such that the lowermost end of the pipe section canbe gripped and lined up with the uppermost end of the pipeline at thepipe connecting station, ix) unlock the second block from the tower, x)connecting the lowermost end of the pipe section to the uppermost end ofthe pipeline, xi) hoist the second block to the uppermost position whilethe pipe section is connected to the pipeline, xii) couple the firstblock and second block, xiii) grip the uppermost end of the pipe sectionwith the traveling clamp, xiv) release the pipeline from the pipeconnecting station and from the static clamp, while holding theuppermost end of the pipeline and supporting it with the traveling clampwith the traveling block in an uppermost position on the tower.
 9. Themethod according to claim 8, wherein the second block is moved from itslowermost position to its uppermost position on the tower and thenconnected to te first block within a time span that is equal or lessthan the time span for connecting the lowermost end of the pipe sectionto the uppermost end of the pipeline.
 10. The method according to claim8 or 9, wherein the traveling clamp is released from the pipe sectionafter the pipe section is gripped at the pipe connecting station.
 11. Ahoisting device, preferably for a marine pipe laying system, comprising:a tower with a tower top side provided with cable pulleys, a travelingblock which is displaceably attached to the tower and which is providedwith cable pulleys and holding means for holding a load, hoisting meanscomprising a hoisting cable and a winch, the hoisting cable being guidedover the cable pulleys on both the tower top side and the travelingblock, wherein the traveling block is moveable with respect to the towerby means of the hoisting means, characterized in that the travelingblock comprises a first block and a second block, both provided withcable pulleys, the first block being provided with the holding means,wherein the first block and the second block are adapted to bereleasably coupled, in which coupled state of the first block and secondblock a higher load can be supported than in an unlocked state and inwhich coupled state of the first block and second block they can travelalong the tower as a unit, and wherein the second block is provided withlocking means for locking it to a lower side of the tower, such that thefirst block can travel in an upward direction along the tower while thesecond block remains stationary with respect to the tower.
 12. A methodfor hoisting a load with a hoisting device according to claim 11, themethod comprising an operation cycle in which: a first load is grippedby the traveling clamp with the traveling block consisting of thecoupled first block and second block in an uppermost position on thetower; the first load is lowered by lowering the coupled together firstblock and second block by means of the hoisting means to a lowermostposition on the tower where the traveling clamp is preferably releasedfrom the first load which is handed over to a load handling device;wherein the second block is locked to the tower by means of the lockingmeans, the first block alone is hoisted from the lowermost position tothe uppermost position by means of the hoisting means, after which thefirst block is used for an intermediate operation after which the secondblock is unlocked from the tower and hoisted to the uppermost positionwhere it is coupled to the first block.
 13. A method for connecting afirst object and a second object at a connecting station wherein use ismade of a device according to claim 11, the method comprising thefollowing steps: i) holding the first object and supporting it with thetraveling clamp with the traveling block in an uppermost position on thetower, ii) lowering the first object by lowering the coupled first blockand second block by means of the hoisting means to a lowermost positionon the tower, iii) gripping the first object with gripping means at theconnecting station, iv) locking the second block to the tower by meansof the locking means, v) hoisting the first block from the lowermostposition to the uppermost position by means of the hoisting means, vi)gripping with the traveling clamp the second object, vii) lowering thefirst block with the second object by means of the hoisting means suchthat the second object is delivered to the connecting station andgripped by its gripping means, viii) releasing the traveling clamp fromthe second object, ix) unlock the second block from the tower, x)connecting the second object to the first object, xi) hoist the secondblock to the uppermost position while connecting the second object tothe first object, xii) couple the first block and second block, xiii)grip the connected first and second object with the traveling clamp,xiv) release the connected first and second object from the connectingstation, while holding them with the traveling clamp with the travelingblock in an uppermost position on the tower.
 14. The method according toclaim 13, wherein the traveling clamp is released from the second objectif after the second object has been gripped by the gripping means of theconnecting station.